1 2 Pore Pressure and Sediment 

 Density Measurements 

 at SUPERTANK 1 



Introduction 



Background 



Pore pressure and sediment density measurements were undertaken as part 

 of the SUPERTANK Laboratory Data Collection Project to complement 

 measurements of wave transformation and beach evolution. Pore pressure 

 measurements may be used to test coupled models of wave interaction with 

 permeable seabeds. Sediment density measurements may be used to relate 

 mass flux to volume flux for models of cross-shore sediment transport. 



The large-scale tests in the SUPERTANK project using prototype sands 

 provided an opportunity to make in-place relative density measurements in the 

 nearshore in a controlled environment. There may be significant variations in 

 the relative density across the profile. On the berm and dune, relative density 

 is anticipated to be lower than on the subaerial portions of the profile. This 

 suggests that a volume of sand eroded from the berm or dune does not result 

 in an equal volume of accretion on the subaerial profile. For a clean uniform 

 sand, porosity can vary from approximately 0.29 to 0.5. This can lead to a 

 70-percent increase in volume from the most dense to the most loose state. 

 This significant change in volume should be considered in beach profile and 

 shoreline change modeling. 



The degree of packing of a granular sediment can significantly influence 

 both the volume occupied by the sediment and the strength of the sediment. 

 Laboratory investigations have shown that stiffness and strength properties of 

 a wide range of granular materials are similar if they have similar relative 



234 



'Written by Charles K. Sollitt, William G. McDougal, David R. Standley, Terence L. Dibble, 

 and William H. Hollings, Oregon State University. 



Chapter 12 Pore Pressure and Sediment Density Measurements 



